117 



On closer examination of the filamentous algae there proved 

 to be two different types present in the tissue at the same time 

 (Fig. 43 — 45, drawn after living material). The last one (Fig. 45) 

 consisting of long, 5 — 6 (Jt. thick, unbranched filaments with girdle- 

 shaped chloroplast appeared free in the aquarium as well as in the 

 sponge tissue. I think it to be Ulothrix subtilissima . The other 

 one (Fig. 43, 44), however, was never free in the aquarium but 

 only to be found in the sponge tissue. As one can see from the 

 illustrations (Fig. 43, 44), it consisted of often very irregularly 

 branched filaments, consisting of cells which could have all sorts 

 of shapes from cylinder- to almost ball-shape. The chlorophyll 

 was scattered all over the cell without any regularity — probably 

 in a great number of chromatophores, while very likely each cell 

 contained one nucleus. The filaments were about 8 — 9 /^ thick. 

 As with a view to my other investigations I could not spend 

 much time on studying these infecting algae, I have not been 

 able to discover their mode of reproduction (nor of the other 

 filamentous alga). Nevertheless I want to draw attention to the 

 fact that this alga, given in Fig. 43 and 44, is much like the 

 Trentepo hHa spongpphila, which professor Weber and Mrs. Weber- 

 Van BossE (64) found in 1890 also in the tissue of Ephydatia 

 fluviatilis , but of specimina originating from a lake on Sumatra. 



Finally I want to speak about the unicellular alga which, as 

 mentioned, appeared either alone or with the two filamentous 

 ones in the tissue of Ephydatiae. Where of course the latter were 

 situated between the amoebocytes, the unicellular one occurred 

 just within the amoebocytes, mostly free in the protoplasm, but 

 sometimes also in different stages of digestion within food- vacuoles. 

 The alga is shown in Fig. 46 — 52 (drawn after living material). 

 The shape was oval, the diameter 5,5 — 7/tt. The cell contained: 

 a chloroplast lining the wall, which let the centre of the cell free 

 and seemed to be one time single and another time composed of 

 several parts ; next a rather big refractive globule and a number 

 of small refractive points, which, with different adjusting of the 

 microscope, were one time lilac-brown and another time blue-green. 

 The wall was rather thin. I have also found a stage of division 



